Telephone system



May 12, 1936. i I A,BQNOM[ 2,040,291

TELEPHONE SYSTEM Filed Nov. 25, 1952 2 Sheets-Sheet. l

PULA RIZED INVENTOR E A. BONOM/ ATmRA/Ek May 12, 1936. F, BQNQN" 2,040,291

TELEPHONE SYSTEM Filed Nov. '25, 1932 2 Sheets-Sheet 2 him.

/N l/E N TOR F. A. BONOM/ A TTORNE V Patented May 12, 1936 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Felix A. Bonomi, St. Albans, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York This invention relates to telephone systems and particularly to improvements in private branch exchange systems.

The object of the invention is to simplify the arrangement at a private branch exchange for preventing unauthorized connections to distant exchanges from being made by private branch exchange subscribers.

Heretofore systems have been provided whereby if a connection is attempted by a subscriber to a zone to which he is not entitled to make connection the subscribers line is disconnected from the attempted connection and transferred to a tone source which sends a tone to the subscriber to remind him that the attempted call is non-permissible. Other systems have been provided in which when connections are extended to a central ofiice over a trunk and this call requires separate supervision by the private branch exchange operator a lamp is lighted at the operators position to permit the operator to supervise the connection. Other systems have also been provided in which if all the trunks to a certain ofiice are busy the call is routed through other trunks and oflices to the desired ofi'ice.

the call is answered at the toll office to which it is extended. Current of a certain polarity is there-' by sent back over the trunk incoming to the private branch exchange. This current causes a relay to operate at the exchange to release the toll connection and to transfer the calling subscribers line to a branch line terminating at a private branch exchange operators position.

It is another feature of this invention to provide means whereby in the establishing of a plurality of toll connections the transfer from such toll connections of the associated subscribers lines may be made to a common branch line leading to a single operators position.

The invention has been shown in the accompanying drawings in which Fig. 1 shows the equipment at a private branch exchange embodying features of the invention, while Fig. 2 shows the equipment partly in diagrammatic form at a main oflice and at a toll ofiice. A trunk between the main office and the toll oflice is illustrated to which connections are not permitted by subscribers at the private branch exchange.

Referring now to the drawings a private branch 55 exchange subscribers set has been illustrated at I connected through automatic switching mechanisms, illustrated by box 2, and terminating in the trunk circuit 3 incoming to the private branch exchange A. This trunk circuit 3 in turn terminates at the main oflice B in automatic connect- 5 ing means, illustrated by box I00, having access to subscribers lines in the main oilice B such as line IUUA and to trunk circuits such as l0! ending in a jack I02 at a toll operators position in the toll oflice C where a toll operators cord I03 10 has been shown in diagrammatic form. The incoming trunk circuit 3 is also connected with a branch circuit 4 terminating in a jack 5 at a private branch exchange operators position, where a cord circuit 6 is shown in diagrammatic 15 form. If a connection is attempted by the subscriber at l for extension to the toll ofiice over a trunk llll, the automatic equipment at 2 is actuated to select an incoming trunk circuit such as 3, and then by a series of dial impulses the 20 equipment at I00 is operated to select a trunk such as lfll. When the toll operator at I03 answers this call battery is reversed over the trunk line towards the private branch exchange, and the connection from the calling subscriber 5 at I is transferred to the branch circuit 4 for answering by the private branch exchange operator. Description will now be made of such a call.

When the subscriber at I has operated the 30 automatic equipment 2 to select the trunk circuit 3 a circuit is completed from battery through the winding of relay l0, make-before-break contacts of relay H, lower outer armature and back contact of relay l2, winding of the polarized relay 5 I3 over the ring conductors through the calling subscribers loop back over the tip conductor, upper outer armatures and back contacts of relays l2 and II to ground. This causes the operation of relay l0. Relay H1 in operating closes a short 40 circuit for the tip and ring conductors leading to the equipment I 00 from the tip conductor, lower winding of relay |5, upper outer armature and front contact of relay I0, lower inner armature and front contact of relay ID to the ring' 5 conductor. As soon as the equipment at 00 has been seized, battery and ground is connected to the ring and tip conductors respectively through the usual line relay in this equipment. This causes the operation of relay I5. This relay in turn closes an obvious circuit for the operation of relay l6. This latter relay closes an obvious circuit for the operation of relay H. Relay ll completes the connection between the tip and ring conductors from the calling subscriber to equipment I00. The tip connection is now extended through the upper inner armature and front contact of relay I I, upper winding of relay I5, upper make-before-break contacts of relay I0, while the ring connection is extended through the lower outer armature and front contact of relay II. The operation of relay II disconnects the winding of relay II) from the calling subscrib ers loop causing this relay to release, while relay I5 is maintained operated to maintain relays I6 and II operated. Relay II in operating also closes an obvious circuit for the operation of relay which closes a connection to ground-atits armature and front contact for the sleeve lead leading to the automatic equipment at12, to maintain preceding switches operated.

The calling subscriber may now control the line relay in equipment Iflll to pulse for the selection in the usual manner of a subscriber such as the one connected to line IEIUA in the main office B or as in the case assumed to pulse for the :selection .in the same ;manner for a trunk 'IEII leading to the toll .ofiice C. When this trunk is seized battery and ground are connected to the ring and :tip conductors back over the calling subscribers loop through the windings of relay IM. This relay operates and closes an obvious circuit for the lighting of lamp I05 to indicate :that a call ;is present on this trunk. The operator .now inserts her plug 166 of a cord I93 into jack I102 thereby closing acircuit from battery, tsleeve terminals of plug I06 and jack I32 to ground through the winding of relay I08. This relay in operating opens the connections from :the :tip andring conductors through the'windings of relay I04, causing this relay to release .and thereby extinguishes lamp Hi5. Relay I04 when originally operated closed 'an obvious circuit for theioperation of relay III] which in turn :closes a connection to ground 'for' the sleeve lead 'to maintain the switches in equipment IElil operated. Relay 'I I0 is now maintained operated under control of relay I 08. It will be noted that the .battery connections through the cord I03 are :reversed for the tip and ring conductors over trunk I02 ileading towards the incoming end of the trunk. Relay I3 inserted in series with the vg-ring conductor will now operate as it 'is polarlay I3, lower inner armature and front contact .of relay "II to ground. Relay I2 closes a locking circuit :for itself through its upper inner armature and front contact to the ground on the :sleeve leads supplied by relay IT. The tip and ring conductors leading to the toll office are now opened at the upper and lower outer armatures .and back contacts of relay 12 so as to signal to the toll operator that this connection is 'not per mitted through the release of the usual super-visory relay in the cord circuit. The tip and ring conductors and sleeve conductor from the calling subscriber at I through the equipment at 2 are then transferred to the tip and ring and sleeve conductors 20 leading to the branch circuit 4.

A connection is now completed from battery and ground through the windings of relay 2! in the branch circuit 4 over the upper inner armature and back contact of relay 22 for the tip conductor, while the ring conductor is extended through' the lower make-before-break contacts of relay 22. Relay 2! in operating :closes aconnection at its upper outer armature 'and front contact to .ground for the sleeve ilead to maintain the switches in the equipment 2 operated. Another obvious circuit is closed by relay 2I for the operation of relay 23. Relay 23 in operating closes an obvious circuit for relay 24!. This latter relay in operating closes a connection to ground at its upper armature and front contact for the sleeve lead and a circuit for the lighting of lamp 26 from battery, lower inner armature and front contact of relay 24, the lower outer armature and back contact of relay 22, lamp 26 to ground. The lighted lamp '26 notifies the private branch exchange operator that .a call is waiting on this line. She will then insert plug 28 of a cord 6 into the jack 2% of the branch circuit 4. This closes an obvious circuit for the operation of relay 22. Relay 22 in operating opens the circuit for lamp 26 to extinguish it and reverses connection from battery and ground from relay 2I to the tip and ring conductors to maintain the battery connections over the line to the calling subscriber in the usual direction for talking. Relays 21, 23 and 24 are maintained operated as long as the connection remains established. It should be noted that on the operation of relay I2 "the relays I5, I 5, II and H were released and on the operation of relay 22 relay I3 was released. Talking battery for the calling subscribed is supplied through the windings of relay2I while the talking battery for the private branch exchange operator is supplied through the usual batteryin the cord .6, condensers 30 and 3| supplying the talking connection between the two parties.

When the calling subscriber releases the connection, relay 2i is released causing the release of the switching equipment 2 and thereleaseof the remaining relays 22, 23 and 24, while relay 24 when released opens the non-conducting shunt established on its operation at its lower outer armature and front contact through repeating coil 32, thereby signaling the private branch exchange operator in the usual manner in the cord circuit that the calling subscriber has disconnected.

What is claimed is:

1. In a telephone system,-a first ofiice, a second ofiice, a calling subscribers line terminating in said first oifice, an operators position in said first oifice, a subscribers line terminating in saidsec- 0nd office, a first trunk connecting said first and second offices, a third office, a second trunk connecting the second and third ofiices, a source of current at said third office, means for establishing a connection from the calling subscriber to the subscriber in the second office over said first trunk, means for establishing a connection from the subscriber in the first ofiice to said third ofiice over said trunks, means for connecting said source of current to said second trunk, and means reponsive to the establishing of a connection from the subscriber'in said first ofiice to said third ofiice and to the connection of said source of current to the second trunk for disconnecting said first trunk from said calling subscribers line and for connecting said calling subscribers line to said operators position.

2. In a telephone system, a first office, a second ofiice, a calling subscribers line terminating .in said first office, a trunk connecting said ofiices, a subscribers line terminating in said second ofiice, a second trunk terminating in said second ofiice, an operators position in said first ofiice, means for establishing connection from the calling subscriber to the subscriber in the second ofiice over the first mentioned trunk, means for establishing a connection from the calling subscriber to the second trunk over the first trunk, a source of current, means for establishing a connection between said source of current and said second trunk, and means responsive to current from said source connected to said second trunk for disconnecting said first trunk from the calling subscribers line and for connecting said calling subscribers line to said operators position.

3. In a telephone system, a first oifice, a second ffice, a calling subscribers line terminating in said first ofiice, an operators position in said first oflice, a subscribers line terminating in said second office, a first trunk connecting said first and second offices, a third office, a second trunk connecting the second and third offices, a source of current at said third ofiice, means for establishing a connection from the calling subscriber to the subscriber in the second oflice over said first trunk, means for establishing a connection from the subscriber in the first office to said third ofllce over said trunks, a signal at said third office associated with said second trunk, means responsive to the connection from the subscriber at the first office to said third oflice over said trunks for actuating said signal, means for connecting said source of current to said second trunk, and means responsive to the establishing of a connection from the subscriber in said first ofiice to said third oifice and to the connection of said source of current to the second trunk for disabling said signal and for disconnecting said first trunk from said calling subscribers line and for connecting said calling subscribers line to said operators position.

4. In a telephone system, a first ofi'ice, a second ofiice, a calling subscribers line terminating in said first office, an operators position in said first office, a signal at said operators position, a subscribers line terminating in said second ofiice, a first trunk connecting said first and second offices, a third ofiice, a second trunk connecting the second and third ofiices, a source of current at said third ofiice, means for establishing a connection from the calling subscriber to the subscriber at the second office over said first trunk, means for establishing a connection from the subscriber at the first oifice to said third oflice over said trunks, means for connecting said source of current to said second trunk, and means responsive to the establishing of a connection from the subscriber in said first office to said third ofiice and to the connection of said source of current to the second trunk for disconnecting said first trunk from said calling subscribers line and for connecting said calling subscribers line to said operators position and actuating said signal.

5. In a telephone system, a first ofiice, a second office, a calling subscribers line terminating in said first office, an operators position in said first ofiice, a subscribers line terminating in said second ofiice, a plurality of trunks in said first oflice having conductors outgoing to said second office, a branch line terminating at said operators position and connectable to any one of said trunks at said first office, a third office, another trunk connecting the second and third ofilces, a source of current at said third ofiice, means for establishing a connection from the calling subscriber to the subscriber in said second ofiice over the outgoing conductors of any one of said first-mentioned trunks, means for establishing a connection from the subscriber in the first oflice to said third office over the outgoing conductors of any one of said first-mentioned trunks and over said second-mentioned trunk, means for connecting said source of current to said secondmentioned trunk and means responsive to the establishing of a connection from the subscriber in said first oifice to said third ofiice and to the connection of said source of current to said second-mentioned trunk for disconnecting the calling subscribers line from the outgoing conductors of the trunk used in the connection and for connecting the calling subscribers line through the branch line to the operators position.

6. In a telephone system, a first office, a second office, a calling subscribers line terminating in said first oflice, a plurality of trunks in said first oifice having outgoing conductors terminating in said second oflice, a branch line connectable to any one of said trunks at said first office, a subscribers line terminating at said second oflice, another trunk outgoing from said second ofiice, means for establishing a connection from the calling subscribers line to the subscriber in the second ofiice over the outgoing conductors of any one of said first-mentioned trunks, means for establishing a connection from the calling subscribers line to the second-mentioned trunk over the outgoing conductors of any one of said first-mentioned trunks, a source of current, means for establishing a connection between said source of current and said second-mentioned trunk, and means responsive to current from said source connected to said second-mentioned trunk for disconnecting the calling subscribers line from the outgoing conductors of the trunk used in the connection between the two ofiices and for connecting said subscribers line to the branch line.

FELIX A. BONOMI. 

